Handle vblank interrupts on the master SH2

Using the m68k for that was prone to race conditions: occasionally the ticcount would go backwards
viciious · Apr 30, 2021 · 427cf1a · 427cf1a
1 parent cf67e91
commit 427cf1a
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Showing 4 changed files with 13 additions and 7 deletions.
diff --git a/32x.h b/32x.h
@@ -47,7 +47,8 @@
 #define MARS_SYS_COMM6      (*(volatile unsigned short *)0x20004026)
 #define MARS_SYS_COMM8      (*(volatile unsigned short *)0x20004028) /* controller 1 current value */
 #define MARS_SYS_COMM10     (*(volatile unsigned short *)0x2000402A) /* controller 2 current value */
-#define MARS_SYS_COMM12     (*(volatile unsigned long *)0x2000402C)  /* vcount current value */
+#define MARS_SYS_COMM12     (*(volatile unsigned short *)0x2000402C)
+#define MARS_SYS_COMM14     (*(volatile unsigned short *)0x2000402C)
 
 #define MARS_PWM_CTRL       (*(volatile unsigned short *)0x20004030)
 #define MARS_PWM_CYCLE      (*(volatile unsigned short *)0x20004032)

diff --git a/crt0.s b/crt0.s
@@ -456,6 +456,10 @@ master_vbi:
         nop
 
         ! handle V IRQ
+        mov.l   vblank_count_ptr,r1
+        mov.l   @r1,r0
+        add     #1,r0
+        mov.l   r0,@r1
 
         mov.l   @r15+,r1
         mov.l   @r15+,r0
@@ -465,6 +469,8 @@ master_vbi:
         .align  2
 mvi_mars_adapter:
         .long   0x20004000
+vblank_count_ptr:
+        .long   _vblank_count
 
 !-----------------------------------------------------------------------
 ! Master H Blank IRQ handler

diff --git a/marsnew.c b/marsnew.c
@@ -39,6 +39,8 @@ const int COLOR_WHITE = 0x04;
 int		activescreen = 0;
 short	*dc_colormaps;
 
+int		vblank_count = 0;
+
 extern int 	debugmode;
 
 static volatile pixel_t	*framebuffer = &MARS_FRAMEBUFFER + 0x100;
@@ -107,6 +109,8 @@ void Mars_Init(void)
 		palette[i] = 0;
 	palette[COLOR_WHITE] = 0x7fff;
 
+	MARS_SYS_INTMSK |= 1 << 3; // enable vblank interrupts
+
 	MARS_SYS_COMM4 = 0;
 }
 
@@ -300,7 +304,7 @@ int I_ReadControls(void)
 
 int	I_GetTime (void)
 {
-	return MARS_SYS_COMM12;
+	return vblank_count;
 }
 
 /*

diff --git a/src-md/crt0.s b/src-md/crt0.s
@@ -124,7 +124,6 @@ init_hardware:
         beq.b   3f                  /* no mouse */
         move.w  #0xF001,0xA1512A    /* mouse in port 2 */
 3:
-        move.l  #0,0xA1512C         /* clear the vblank count */
 
 | allow the 68k to access the FM chip
         move.w  #0x0100,0xA11100    /* Z80 assert bus request */
@@ -389,10 +388,6 @@ vert_blank:
         bsr.b   get_pad
         move.w  d2,0xA1512A         /* controller 2 current value */
 1:
-        move.l  0xA1512C,d0
-        addq.l  #1,d0
-        move.l  d0,0xA1512C         /* increment the vblank count */
-
         tst.w   gen_lvl2
         beq.b   2f
         lea     0xA12000,a0